Ultrasonic S-Detect mode for the evaluation of thyroid nodules: A meta-analysis

Objectives: This meta-analysis aimed to evaluate the value of ultrasonic S-Detect mode for the evaluation of thyroid nodules. Methods: We searched PubMed, Cochrane Library, and Chinese biomedical databases from inception to August 31, 2021. Meta-analysis was conducted using STATA version 14.0 and Meta-Disc version 1.4 software. We calculated the summary statistics for sensitivity (Sen), specificity (Spe), summary receiver operating characteristic curve, and the area under the curve, and compared the area under the curve between ultrasonic S-Detect mode and thyroid imaging report and data system (TI-RADS) for the diagnosis of thyroid nodules. As a systematic review summarizing the results of previous studies, this study does not need the informed consent of patients or the approval of the ethics review committee. Results: Fifteen studies that met all inclusion criteria were included in this meta-analysis. A total of 924 thyroid malignant nodules and 1228 thyroid benign nodules were assessed. All thyroid nodules were histologically confirmed after examination. The pooled Sen and Spe of TI-RADS were 0.89 (95% confidence interval [CI] = 0.85–0.91) and 0.85 (95% CI = 0.78–0.90), respectively; the pooled Sen and Spe of S-Detect were 0.88 (95% CI = 0.85–0.90) and 0.73 (95% CI = 0.63–0.81), respectively. The areas under the summary receiver operating characteristic curve of TI-RADS and S-Detect were 0.9370 (standard error [SE] = 0.0110) and 0.9128 (SE = 0.0147), respectively, between which there was no significant difference (Z = 1.318; SE = 0.0184; P = .1875). We found no evidence of publication bias (t = 0.36, P = .72). Conclusions: Our meta-analysis indicates that ultrasonic S-Detect mode may have high diagnostic accuracy and may have certain clinical application value, especially for young doctors.


Introduction
Thyroid nodules are one of the most common diseases of the endocrine system. According to statistics, 19% to 68% of people have thyroid nodules, but the malignancy rate is relatively low, approximately 3% to 10%. [1] In recent years, the global incidence of thyroid cancer has been increasing significantly, and thyroid nodules are the most common clinical manifestations of thyroid cancer. The most challenging problem for clinicians is differentiation between benign and malignant thyroid nodules. Accurate differentiation of benign and malignant thyroid nodules is crucial to the selection of patient treatment. Ultrasound is widely accepted as the preferred imaging screening method for thyroid nodules because it is noninvasive, does not require ionizing radiation, and has a low cost. In 2017, the American College of Radiology proposed the latest version of TI-RADS classification, American College of Radiology TI-RADS, based on largescale, evidence-based clinical validation, which greatly improves the objectivity of ultrasound diagnosis. [2] However, the subjective influence of ultrasonic physicians on TI-RADS interpretation cannot be avoided. The evaluation of thyroid nodules by different sonographers is subjective and different, and the diagnosis results are easily affected by ultrasonic instruments, surrounding environment, image quality, and other factors. [3] Computer-aided diagnosis (CAD) technology is one of the hotspots of artificial intelligence and modern medical research. With the advancement of artificial intelligence technology, researchers have developed ultrasound-based commercial CAD systems. [4,5]  based on the TI-RADS grading and classification standard learning for ultrasonic images of thyroid nodules. This technology can automatically detect and analyze information such as thyroid nodule boundary, shape, and echogenicity. It can overcome the interference of human factors and objectively distinguish benign and malignant thyroid nodules. [6] Previous studies have shown that ultrasonic S-Detect mode avoids subjective conclusions, improves diagnostic efficiency, and detects thyroid cancer with high sensitivity. [7,8] However, the results of these studies contradict each other, and the sample populations are too small. This analysis is designed to assess the diagnosis value of ultrasonic S-Detect mode in identifying malignant gland nodules.

Literature search
We searched PubMed, Web of Science, Cochrane Library, and Chinese biomedical databases from inception through August 31, 2021. The following keywords and MeSH terms were used:   [24] 2020 Hungary English ["thyroid cancer" or "thyroid neoplasm" or "thyroid tumor" or "thyroid nodule"] and ["S-Detect"]. We also performed a manual search to find other potentially suitable articles.

Selection criteria
The following 4 criteria were required for each study: the study design must be a clinical cohort study or diagnostic test, the study must relate to the ultrasonic S-Detect mode accuracy with respect to the differential diagnosis of benign and malignant thyroid nodules, all thyroid nodules must have been histologically confirmed after ultrasonic S-Detect mode, and published data in the fourfold (2 × 2) tables must be sufficient. If the study did not meet all of these inclusion criteria, it was excluded. When authors published >1 study using the same subjects, only the most recent publication or the publication with the largest sample size was included.

Data extraction
Relevant data were systematically extracted from all included studies by 2 researchers using a standardized form. The researchers collected the following data: the first author's surname, year of publication, language of publication, study design, sample size, number of lesions, source of the subjects, gold standard, and diagnostic accuracy. The true positives, true negatives, false positives, and false negatives in the 4-fold (2 × 2) tables were also collected.

Quality assessment
Methodological quality was independently assessed by 2 researchers using the quality assessment of studies of diagnostic accuracy studies (QUADAS) tool. [9] The QUADAS criteria included 14 assessment items. Each of these items was scored as "yes" (2), "no" (0), or "unclear" (1). The QUADAS score ranged from 0 to 28, and a score of ≥22 indicated good quality.

Statistical analysis
The STATA version 14.0 (Stata Corp, College Station, TX), Meta-Disc version 1.4 (Universidad Complutense, Madrid, Spain), and MedCalc version 15.2.2 (MedCalc Software, Ostend, Belgium) software packages were used for meta-analysis. We calculated the pooled summary statistics for sensitivity (Sen) and specificity (Spe) with their 95% confidence interval (CI). The summary receiver operating characteristic (SROC) curve and corresponding area under the curve were obtained. We compared the 2 area under the curves of TI-RADS and S-detect. We built Begger funnel plots and Egger linear regression tests to assess publication bias.

Ethical statement
As a systematic review summarizing the results of previous studies, this study does not need the informed consent of patients or the approval of the ethics review committee.

Characteristics of included studies
Initially, the keywords identified 40 articles. We reviewed the titles and abstracts of all articles and excluded 17; full texts and data integrity were also reviewed and 8 more were also excluded. Finally, 15 studies that met all inclusion criteria were included in this meta-analysis. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Figure 1 shows the selection process. A total of 924 thyroid malignant nodules and 1228 thyroid benign nodules were assessed. We summarize the study characteristics and methodological quality in Table 1. The QUADAS scores of all included studies were of ≥22.

Discussion
In recent years, the incidence of thyroid disease has increased annually. [25] Ultrasound is the preferred imaging method for screening this disease, and it has greatly increased the detection rate of thyroid nodules. Differential diagnosis of thyroid nodules mainly involves the grade of ultrasound, microcalcification, irregular edges, and an aspect ratio of >1 for thyroid cancer. This approach has high diagnostic specificity. [26][27][28] However, the ultrasound diagnosis is largely dependent on the experience and skill of the operator, and there is no single ultrasound characteristic or feature combination that can reliably predict the characteristics of malignant thyroid tumors. In this way, diagnoses vary considerably among different observers due to both subjective and objective factors. Diagnoses made by ultrasound doctors who lack experience may cause the patient to undergo unnecessary puncture biopsy or surgery. [29] Ultrasonic S-Detect mode is a new technique for diagnosing thyroid nodules using artificial intelligence. It is based on a deep learning algorithm, characteristics of segmentation, feature analysis of the lesions and description of unstructured data thyroid images through image dimension reduction, and labeling, such as use of the calculation process final output for composition, direction, shape, the echo intensity, sponginess, edges, calcification, and benign and malignant diagnosis using structured data, such as the last of the dichotomy classification diagnoses of benign and malignant tumor. [30] Because thyroid nodule ultrasound images are easy to obtain and have acceptable quality, they can be used to assist in the diagnosis made by primary doctors. This can reduce misdiagnosis, avoid missed diagnosis, prevent unnecessary puncture biopsy, reduce the risk of overdiagnosis and treatment, and improve the diagnosis accuracy of thyroid nodules. [31] However, ultrasonic S-Detect mode cannot replace traditional ultrasound; it can only supplement it. Although ultrasonic S-Detect mode is considered a potentially useful auxiliary tool, it still has not seen extensive application. It is still in its starting phase with respect to the diagnosis of thyroid disease.
In the present meta-analysis, we systematically evaluated the technical performance and accuracy of ultrasonic S-Detect mode for differential diagnosis of benign and malignant thyroid nodules. Ultrasonic S-Detect mode may be a good tool for the diagnosis of thyroid nodules. However, our research has certain limitations. First, this was mostly a single-center study, and the sample size was small. In addition, the traceability of meta-analysis may introduce some bias into the selection of subjects. Here, the ultrasonic S-Detect mode was analyzed with respect to 2-dimensional ultrasound images. We observed a difference in ultrasonic S-Detect mode diagnostic compliance across different standard cuts. There is a certain error.
In conclusion, our meta-analysis suggests that ultrasonic S-Detect mode may have high diagnostic accuracy in distinguishing benign and malignant thyroid nodules, and ultrasonic S-Detect mode may be a good tool for the diagnosis of thyroid nodules.